﻿// NameFilter.cs
//
// Copyright 2005 John Reilly
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.


using System;
using System.Collections;
using System.Text.RegularExpressions;

namespace Flowertwig.Utils.Compression.General
{
    /// <summary>
    /// NameFilter is a string matching class which allows for both positive and negative
    /// matching.
    /// A filter is a sequence of independant <see cref="Regex"></see> regular expressions separated by semi-colons ';'
    /// Each expression can be prefixed by a plus '+' sign or a minus '-' sign to denote the expression
    /// is intended to include or exclude names.  If neither a plus or minus sign is found include is the default
    /// A given name is tested for inclusion before checking exclusions.  Only names matching an include spec 
    /// and not matching an exclude spec are deemed to match the filter.
    /// An empty filter matches any name.
    /// </summary>
    public class NameFilter
    {
        /// <summary>
        /// Construct an instance based on the filter expression passed
        /// </summary>
        /// <param name="filter">The filter expression.</param>
        public NameFilter(string filter)
        {
            this.filter = filter;
            inclusions = new ArrayList();
            exclusions = new ArrayList();
            Compile();
        }

        /// <summary>
        /// Test a string to see if it is a valid regular expression.
        /// </summary>
        /// <param name="e">The expression to test.</param>
        /// <returns>True if expression is a valid <see cref="System.Text.RegularExpressions.Regex"/> false otherwise.</returns>
        public static bool IsValidExpression(string e)
        {
            bool result = true;
            try
            {
                Regex exp = new Regex(e, RegexOptions.IgnoreCase | RegexOptions.Singleline);
            }
            catch
            {
                result = false;
            }
            return result;
        }

        /// <summary>
        /// Test an expression to see if it is valid as a filter.
        /// </summary>
        /// <param name="toTest">The filter expression to test.</param>
        /// <returns>True if the expression is valid, false otherwise.</returns>
        public static bool IsValidFilterExpression(string toTest)
        {
            bool result = true;

            try
            {
                string[] items = toTest.Split(';');
                for (int i = 0; i < items.Length; ++i)
                {
                    if (items[i] != null && items[i].Length > 0)
                    {
                        string toCompile;

                        if (items[i][0] == '+')
                            toCompile = items[i].Substring(1, items[i].Length - 1);
                        else if (items[i][0] == '-')
                            toCompile = items[i].Substring(1, items[i].Length - 1);
                        else
                            toCompile = items[i];

                        Regex testRE = new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Singleline);
                    }
                }
            }
            catch (Exception)
            {
                result = false;
            }

            return result;
        }

        /// <summary>
        /// Convert this filter to its string equivalent.
        /// </summary>
        /// <returns>The string equivalent for this filter.</returns>
        public override string ToString()
        {
            return filter;
        }

        /// <summary>
        /// Test a value to see if it is included by the filter.
        /// </summary>
        /// <param name="testValue">The value to test.</param>
        /// <returns>True if the value is included, false otherwise.</returns>
        public bool IsIncluded(string testValue)
        {
            bool result = false;
            if (inclusions.Count == 0)
                result = true;
            else
            {
                foreach (Regex r in inclusions)
                {
                    if (r.IsMatch(testValue))
                    {
                        result = true;
                        break;
                    }
                }
            }
            return result;
        }

        /// <summary>
        /// Test a value to see if it is excluded by the filter.
        /// </summary>
        /// <param name="testValue">The value to test.</param>
        /// <returns>True if the value is excluded, false otherwise.</returns>
        public bool IsExcluded(string testValue)
        {
            bool result = false;
            foreach (Regex r in exclusions)
            {
                if (r.IsMatch(testValue))
                {
                    result = true;
                    break;
                }
            }
            return result;
        }

        /// <summary>
        /// Test a value to see if it matches the filter.
        /// </summary>
        /// <param name="testValue">The value to test.</param>
        /// <returns>True if the value matches, false otherwise.</returns>
        public bool IsMatch(string testValue)
        {
            return IsIncluded(testValue) == true && IsExcluded(testValue) == false;
        }

        /// <summary>
        /// Compile this filter.
        /// </summary>
        void Compile()
        {
            if (filter == null)
                return;

            string[] items = filter.Split(';');
            for (int i = 0; i < items.Length; ++i)
            {
                if (items[i] != null && items[i].Length > 0)
                {
                    bool include = items[i][0] != '-';
                    string toCompile;

                    if (items[i][0] == '+')
                        toCompile = items[i].Substring(1, items[i].Length - 1);
                    else if (items[i][0] == '-')
                        toCompile = items[i].Substring(1, items[i].Length - 1);
                    else
                        toCompile = items[i];

                    // NOTE: Regular expressions can fail to compile here for a number of reasons that cause an exception
                    // these are left unhandled here as the caller is responsible for ensuring all is valid.
                    // several functions IsValidFilterExpression and IsValidExpression are provided for such checking
                    if (include)
                        inclusions.Add(new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.Singleline));
                    else
                        exclusions.Add(new Regex(toCompile, RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.Singleline));
                }
            }
        }

        #region Instance Fields
        string filter;
        ArrayList inclusions;
        ArrayList exclusions;
        #endregion
    }
}
